1. Field of the Invention
The present invention relates to a water purifier that is capable of purifying service water (raw water) through a filter and cleaning (back washing) a filter member by passing service water (raw water) through the filter member from an opposite direction.
2. Description of the Related Art
Household water purifiers are widely used to purify raw water through a filter member while directly coupled to a bibcock (a faucet) of a water line. The filter member generates purified water by trapping impurities such as inorganic particles and bacteria contained in the raw water.
Various water purifiers have been proposed in the related art, and the present applicant has also filed a series of patent applications using a constitution described in U.S. Pat. No. 5,192,436 as a basic constitution. FIG. 12 shows a water purifier 101 having a similar basic constitution to that described in U.S. Pat. No. 5,192,436. The water purifier 101 includes an attachment main body 110 attached to a bibcock F of a water line, and a water purification main body 120 that is attached rotatably to the attachment main body 110 to be capable of purifying raw water from the water line into purified water by filtering the raw water. An inflow port 111 to which the bibcock F is coupled so that the raw water flows therein and a purified water outflow port 112 from which the purified water flows are provided on an upper side and a lower side of the attachment main body 110, respectively, while an inflow passage P111 and a purified water outflow passage P112 are provided in the attachment main body 110 to communicate with the inflow port 111 and the purified water outflow port 112, respectively. The water purification main body 120 is constituted by a water purification portion 120A in which a partition wall member 127 packed with a filter member 125 is disposed, and a valve portion 120B that is inserted into and rotatably attached to an attachment hole portion 115 provided in the attachment main body 110. A first flow passage P121 and a second flow passage P122 are provided in the water purification main body 120.
When purified water is caused to flow out of the purified water outflow port 112 (to be referred to hereafter as a water purification mode) in the water purifier 101, the inflow passage P111 and the purified water outflow passage P112 of the attachment main body 110 communicate respectively with the first flow passage P121 and the second flow passage P122 of the water purification main body 120. Further, when the filter member 125 is cleaned, the water purification main body 120 is rotated 180 degrees relative to the attachment main body 110 such that the inflow passage P111 and the purified water outflow passage P112 of the attachment main body 110 communicate respectively with the second flow passage P122 and the first flow passage P121 of the water purification main body 120, whereby waste water flows out from the purified water outflow port 112. Hence, by rotating the water purification main body 120 relative to the attachment main body 110, a water flow path is switched such that water is passed through the water purifier 101 in an opposite direction to the water purification mode, and as a result, the filter member 125 can be cleaned. Thus, a purification capacity of the water purifier 101 can be maintained. Note that cleaning the filter member by passing water through the filter member in an opposite direction to the water purification mode will be referred to hereafter as back washing, and a back washing operation will be referred to as a back washing mode.
However, the water quality of raw water from a water line differs from region to region, and depending on the raw water, impurities may become trapped and adhered to a side where impurities are not normally trapped during back washing of the filter member. From a worldwide viewpoint, differences in the water quality of raw water from region to region are extremely great.